MODELING OF THE COOLING OF SEMICRYSTALLINE POLYMERS DURING THEIR PROCESSING

As a first step for the modelling of the processing of semicrystalline polymers, it is proposed a new overall kinetic model which allows to calculate the evolution of the transformed volume fraction whatever the cooling conditions are. This model derives from initial Avrami-Evans' theory. The transformed volume fraction is calculated as a function of parameters which are measured during crystallizations at a constant cooling rate. This model is easy to use and can be introduced into a more complete thermomechanical calculation. For this purpose we propose to express the energy equation in terms of the enthalpy function. Two applications of our model are presented: the cooling of a polymer sheet (non-flowing polymer) and the cooling of the film on the chill-roll during the cast film extrusion process (flowing polymer).